Papuasian pteridophyte families

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Hemionitidaceae

Small to medium-size terrestrial ferns, rarely epiphytic, rhizome compact and ascending to creeping with spaced fronds, solenostelic or dictyostelic when fronds crowded, young parts protected by dark glossy bristles or by scales. Fronds long-stipitate, or the stalks short with a decurrent lamina, stipes often dark and polished, 2 or 3 ribbon-like vascular bundles at the base, sometimes uniting distally to form one of V- or U- shape, sometimes a single U-shaped bundle throughout, the lamina simple to pinnate, pedate, bipinnate or tripinnate, firm, veins free to variously anastomosing without free included veinlets; the fronds uniform or weakly or strongly dimorphic, the fertile fronds longer with variously contracted lamina. Sporangia spreading irregularly along the veins or confined to a longitudinal band on a vascular commissure between the costa and the margin, or immersed in a submarginal groove, or entirely covering the abaxial surface of contracted pinnae, or in discrete round sori submarginal at the vein ends, exindusiate, paraphyses usually abundant, less often absent, annulus longitudinal interrupted; spores trilete, globose and smooth, to dark with a ridged perispore.

Distribution

A worldwide family of 20 - 25 genera, covering c. 140 - 170 species. In Papuasia there are 7 genera with a total of c. 16 species.

Literature

Copeland, E.B. 1949. Pteridaceae of New Guinea. Philip. J. Sci. 78: 5 - 40.

Holttum, R.E. 1968. A redefinition of the fern genus Taenitis Willd. Blumea 16: 86 - 95.

Holttum, R.E. 1975. A comparative account of the fern genera Syngramma J.Sm. and Taenitis Willd., with discussions on relationships to each other and to other genera. Kew Bull. 30: 327 - 343.

Panigrahi, G. 1975. The genus Pityrogramma (Hemionitidaceae) in Asia. Kew Bull. 30: 657 - 667.

Genera

1a.	Rigid hairs or bristles on rhizome and bases of stipes	2
	Obvious flat scales on rhizome and bases of stipes	5
2a.	Plant an obvious rheophyte on rocks in or by streams; fronds tripinnatifid; sori short but elongate along the end of the veins	Austrogramme (1)
	Plants terrestrial, never rheophytic; fronds simple to pinnate or +/- palmate; sori elongate along the veins or fused into a larger sorus parallel to the costa	3
3a.	Veins free to the margin; fronds simple, on short stipes	Toxopteris (2)
	Veins anastomosing at the margin or more copiously; fronds simple, pinnate or +/- palmate on long stipes	4
4a.	Veins parallel and anastomosing near the margin forming a single series of marginal areoles; sori narrow, the sporangia spread along the veins; fronds mostly +/- palmate, sometimes simple	Syngramma (c. 4)
	Veins freely anastomosing throughout the lamina; sori broad, elongate and parallel to the costa and edge of lamina (lamina may be strongly constricted on fertile fronds), or spreading along the veins; fronds simple to pinnate	Taenitis (6)
5a.	Lower surface of fronds covered with a white or yellowish powder	Pityrogramma (1)
	Lower surface of frond not covered with a waxy powder	6
6a.	Plants epiphytic; lamina pinnate, the pinnae dimidiate; sori round, submarginal at the ends of the veins; rhizome scales clathrate; stipe with 2 vascular bundles, not uniting upwards	Rheopteris (1)
	Plants terrestrial or on rocks by streams; lamina pinnate to tripinnate; sori elongate along the veins; rhizome scales not clathrate; stipe with vascular system in a single U-shaped strand	Coniogramme (2)

Note

Many authors do not recognise the genus Toxopteris as distinct from Syngramma, however the differences in frond shape and venation is correlated with differences in stipe vasculature.

The genus Rheopteris is very anomalous wherever it is placed; the clathrate scales and fleshy rhizome suggest Vittariaceae but this is purely a simple-fronded family. Its systematic position requires further study.

In some treatments this family is included with Cryptogrammitaceae and Sinopteridaceae in an enlarged Adiantaceae, and sometimes in a wider Pteridaceae. This is a very diverse and complex group of genera.

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Updated November 1999 by Jim Croft (jrc@anbg.gov.au)